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Are Your Emails Ending Up on BLACKLISTS or WHITELISTS?

Updated: Jun 5, 2020

Reaching your target audience can be a hard task in a world ruled by automated email marketing campaigns. To overcome this, two concepts directly impact your deliverability: whitelists and blacklists. Knowing and understanding the meaning of these terms allows a sender to enjoy the benefits of whitelists and avoid the disadvantages of blacklists.


Marketers are always strategizing about how they can drive more revenue through email marketing by reengage people who haven’t purchased or interacted with the brand in a while. And for good reason: Consumers who purchase products through email spend 138% more than those that don’t receive email offers. While marketers are aware of the staggering numbers, it’s easy to neglect email best practices and, as a result, end up on a blacklist.

An email blacklist is composed of emails, URLs, domains and IP addresses classified as poor because they are associated with spamming senders. A blacklist is commonly used by mail receivers (ISPs, hosting companies, etc.) to block unwanted mail from bad senders.

However, a legitimate sender who doesn’t adhere to best practices can also be impacted.

Blacklist operators most commonly use networks of spam traps to catch marketers behaving badly. Mailing to spam trap addresses is a signal of poor list hygiene practices, since those addresses don’t belong to real users. Depending on the type of trap mailed (or hit) and the number, senders may get flagged as a bad and end up on a blacklist.

The amount of mail blocked depends on which blacklist a sender ends up on. Some are more impactful than others, depending on which mail receivers use them. Spamhaus, for example, is the most widely known blacklist and is used by some of the major mailbox providers. So, a Spamhaus listing will have a big impact on reputation and delivery of mail.

The best way to avoid the blacklist is to only mail recently-engaged users who have opened or clicked on an email in the last 90 days. We don’t recommend including anyone who hasn’t engaged in over a year as those recipients are at a high risk of hitting recycled spam traps. In addition to the user activity, double opt-in acquisition of leads is a great way to avoid mailing repeatedly to spam trap addresses as they won’t click the confirmation link. We also highly recommend the use of a reCAPtCHA at sign-up to mitigate malicious signups.


Many senders believe that an email whitelist is a permanent, direct path to the inbox at an ISP with no filtering applied. That may have been true in the past, but today they aren’t the magic bullet senders hope for.

A whitelist is a list of email addresses or domain names domains associated with a good sender reputation from which an email blocking program will be less strict with, thus allowing messages to be received.

Whitelists are employed by ISP mail systems to provide benefits associated with increased trust in mail coming from the IP or domain in question. Benefits of whitelisting can include an increased throughout (send more mail faster) and fewer levels of filtering.

To be added to a whitelist, a sender must meet the criteria of the whitelist provider, which generally align with email best practices:

  • Low complaint rates

  • Low/no spam trap hits

  • Low percentage of invalid addresses

  • Authenticated mail

The most well-known whitelists include Return Path Certification (paid, third-party) and Certified Senders Alliance (paid, 3rd party). For example, as a reputable sender, Mapp is CSA accredited.

Even though a sender may be accepted onto a whitelist, ISPs and third-party providers are constantly monitoring traffic and may remove senders who don’t meet certain standards and follow best practices. So, it’s important to maintain good sending practices at all times.

While the whitelists apply to domain and IP level filtering, there is also personal whitelisting at the user level. Personal whitelists are a custom list of email addresses and/or domains from which a subscriber always wants to receive emails. Recipients can whitelist a specific sending email address or a full sending domain, giving them ultimate control over what they receive in their inbox. In this case, all the filters are disabled for whitelisted senders – and as an email marketer, this is your ideal situation.

This article was first published by MAPP. Permission to use has been granted by the publisher.

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